In the case of a slip of a hydraulic friction engagement element engaged by using a line pressure as a source pressure to establish a predetermined gear position of an automatic transmission, it is required to determine whether the slip is caused by a line pressure regulating device, so as to identify a failure component. Therefore, for a vehicle power transmission device including (a) a line pressure regulating device that regulates a hydraulic pressure of a hydraulic fluid discharged from an oil pump to a line pressure and that may become unable to perform the regulation and cause an abnormality resulting in output of a minimum line pressure and (b) an automatic transmission having a predetermined gear position established by engagement of a hydraulic friction engagement element based on the line pressure, a control device is proposed that has (c) an abnormality determination portion detecting a slip of the hydraulic friction engagement element establishing the predetermined gear position at the time of establishment of the predetermined gear position and, if an input torque at the time of occurrence of the slip is equal to or greater than an abnormality determination value defined in advance based on a torque transmittable at the minimum line pressure by the hydraulic friction engagement element establishing the predetermined gear position, making an abnormality determination indicative of a possibility of an abnormality causing the output hydraulic pressure of the line pressure regulating device to be the minimum line pressure (see Patent Document 1). A device known as the line pressure regulating device is a device that performs a regulation of a hydraulic pressure of a hydraulic fluid to a predetermined line pressure while changing an opening area of a discharge flow passage and that may become unable to perform the regulation and cause an abnormality resulting in output of the minimum line pressure while the opening area of the discharge flow passage is maximized.